err... because the caption suggests he's a terrorist?
like when we used to see pix of bin laden, and it said he was a terrorist? so we knew he was a terrorist?
i'm interested in why your question seemed to focus on the cultural references rather than sexuality.
how do we know he's gay? well, he can't be. there aren't any gay muslims. that's if he IS a muslim. maybe he just dresses like that because he wants people to think he's not a terrorist, because there aren't any terrorists who dress like that.
what IS your point about this joke-picture, exactly?